Automated drilling optimization

ABSTRACT

A method implemented by a processor for drilling a borehole includes: inputting drilling parameters used to drill one or more offset boreholes, rate of penetration for the one or more offset boreholes, and one or more lithologies for the one or more offset boreholes; identifying those drilling parameters that correspond to a rate of penetration (ROP) that meets or exceeds a selected ROP threshold for each input lithology; correlating a borehole plan comprising a borehole path to be drilled and one or more assumed lithologies as a function of depth to the one or more lithologies of the one or more offset boreholes; sending the identified drilling parameters to a drill rig controller for each of the assumed lithologies in the borehole plan; and drilling the borehole with the drill rig using the identified drilling parameters for each of the one or more assumed lithologies in the borehole plan.

BACKGROUND

Earth formations may be used for various purposes such as hydrocarbonproduction, geothermal production, and carbon dioxide sequestration.These reservoirs are typically accessed by drilling boreholes throughthe earth to the reservoirs.

A borehole is drilled using a drill bit that is rotated by drill pipescoupled together in series and generally referred to as a drill string.A drill rig disposed at the surface of the earth or at the surface ofthe ocean for ocean drilling applies forces to the drill string and thusto the drill bit for cutting formation rock. The forces may includerotational force or torque for rotating the drill string, weight on thedrill bit, and force due to the flow of drilling fluid internal to thedrill string. The combination of the drill string forces applied to thedrill string result in a rate of penetration into the formation beingdrilled. It would be appreciated by the drilling industry if a methodwas developed that estimates a combination of drill string force valuesor parameters that would improve the rate of penetration and lower thecost of drilling a borehole.

BRIEF SUMMARY

Disclosed is a method for drilling a borehole penetrating the earthusing a drill rig that operates a drill string. The method includes:inputting into a processor (i) drilling parameters as a function ofdepth used to drill one or more offset boreholes, (ii) rate ofpenetration as a function of depth using the drilling parameters for theone or more offset boreholes, and (iii) one or more lithologies as afunction of depth for the one or more offset boreholes; identifying,using the processor, those drilling parameters that correspond to a rateof penetration (ROP) that meets or exceeds a selected ROP threshold foreach input lithology to provide identified drilling parameters;correlating a borehole plan having a borehole path to be drilled and oneor more assumed lithologies as a function of depth to the one or morelithologies of the one or more offset boreholes using the processor;sending the identified drilling parameters to a drill rig controller foreach of the assumed lithologies in the borehole plan; and drilling theborehole with the drill rig using the identified drilling parametersthat provide the ROP that meets or exceeds the selected ROP thresholdfor each of the one or more assumed lithologies in the borehole plan.

Also disclosed is a method for drilling a borehole penetrating the earthusing a drill rig that operates a drill string. The method includes:inputting into a processor (i) drilling parameters as a function ofdepth used to drill one or more offset boreholes, (ii) rate ofpenetration using the drilling parameters for the one or more offsetboreholes, (iii) any drilling dysfunctions that occurred using thedrilling parameters for the one or more offset boreholes, and (iv) oneor more lithologies as a function of depth for the one or more offsetboreholes; identifying, using the processor, those drilling parametersthat correspond to a rate of penetration (ROP) that meets or exceeds aselected ROP threshold for each input lithology to provide identifieddrilling parameters and/or to a minimum number of drill dysfunctions orminimum magnitude of a drilling dysfunction to provide identifieddrilling parameters; correlating a borehole plan having a borehole pathto be drilled and one or more assumed lithologies as a function of depthto the one or more lithologies of the one or more offset boreholes;automatically transmitting identified drilling parameters to a drill rigcontroller for a change in lithology when a depth is reached signifyingthe beginning of an interval of the changed lithology according to theborehole plan; drilling the borehole with the drill rig using theidentified drilling parameters that provide the ROP that meets orexceeds the selected ROP threshold for each of the one or more assumedlithologies in the borehole plan; and sending an override signal fromthe processor to the drill rig controller based on a drillingperformance indicator sensed by a drilling performance sensor.

Further disclosed is an apparatus for drilling a borehole penetratingthe earth using a drill rig that operates a drill string. The apparatusincludes a processor that is configured to: receive (i) drillingparameters as a function of depth used to drill one or more offsetboreholes, (ii) rate of penetration using the drilling parameters forthe one or more offset boreholes, (iii) any drilling dysfunctions thatoccurred using the drilling parameters for the one or more offsetboreholes, and (iv) one or more lithologies as a function of depth forthe one or more offset boreholes; identify those drilling parametersthat correspond to a maximum rate of penetration for each receivedlithology to provide identified drilling parameters; correlate aborehole plan having one or more assumed lithologies as a function ofdepth to the one or more lithologies of the one or more offset boreholesusing the processor; and transmitting the identified drilling parametersthat provide the maximum rate of penetration for each of the one or moreassumed lithologies in the borehole plan to the drill rig for drillingthe borehole.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 illustrates a cross-sectional view of an exemplary embodiment ofa drill string disposed in a borehole penetrating the earth;

FIG. 2 is a top-view of the surface of the earth illustrating theborehole being drilled and several offset boreholes already drilled intothe same or similar formation; and

FIG. 3 is a flow chart for a method for drilling a borehole penetratingthe earth using a drill rig that operates a drill string.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method presented herein by way of exemplification and notlimitation with reference to the figures.

Disclosed are method and associated apparatus for drilling a boreholepenetrating the earth using a drill rig that operates a drill string.The method and apparatus optimize or improve the rate of penetration ofthe drill string into a formation layer being drilled as compared toconventional methods and apparatus. Drilling parameters obtained frompreviously drilled offset boreholes are analyzed to determine which ofthe drilling parameters provide the highest rate of penetration (ROP)and an associated low number and/or magnitude of drilling dysfunctionsfor each of the lithologies through which the offset boreholes weredrilled. A borehole plan is generated using the lithology informationfrom offset boreholes. The borehole plan includes the estimated depthand thickness of each of the lithologies expected to be encounteredwhile the borehole is being drilled. The drilling parameters thatprovided the highest ROP with low drilling dysfunctions areautomatically input into a drill rig controller that controls theoperation of the drill string. In this manner, the ROP of the boreholebeing drilled can be improved with an associated increase inreliability.

Apparatus for implementing the method is now discussed with reference toFIG. 1. In FIG. 1, a cross-sectional view is illustrated of an exemplaryembodiment of a drill string 9 for drilling a borehole 2 penetrating theearth 3, which includes a formation 4 having formation layers 4A-4D.(For illustration purposes, the formation layers are only illustrated onthe right side of the borehole, but are also intended to be illustrativeof the left side.) Each of the formation layers may represent alithology different from a lithology of adjacent layers. The drillstring 9 is made up of a series of drill pipes 8 that are connectedtogether. A drill bit 7 for drilling or cutting into earth is disposedat the distal end of the drill string 9. A drill rig 6 is configured toconduct drilling operations such as rotating the drill string 9 and thusthe drill bit 7 in order to drill the borehole 2. The drill rig 6 isalso configured to control the weight-on-bit applied to the drill bitfor drilling purposes. In addition, the drill rig 6 is configured topump drilling fluid through the interior of the drill string 9 in orderto lubricate the drill bit 7 and flush cuttings from the borehole 2. Adrill rig controller 5 is configured to control various drillingparameters that apply force or energy to the drill string 9 for drillingthe borehole 2. Non-limiting examples of these drilling parametersinclude weight-on-bit, applied drill string torque, and drilling fluidflow rate. A bottomhole assembly (BHA) 10 is disposed on the drillstring 9 generally near the drill bit 7. The BHA 10 may include thedrill bit 7 in some embodiments

In the embodiment of FIG. 1, the BHA 10 includes a borehole surveysensor 11, a drilling performance sensor 12, and a lithology sensor 13.The borehole survey sensor 11 is configured to sense a location of theBHA 10 and thus of the borehole 2. “Location” refers to a trajectory orpath including depth of the borehole 2 that has already been drilled. Itcan be appreciated that the borehole depth may be measured as a truevertical depth in order to accommodate depth measurements of deviated orhorizontal boreholes. Non-limiting embodiments of the borehole surveysensor 11 include a gravity sensor for measuring true vertical depth, amagnetic field sensor for measuring azimuthal orientation, and anaccelerometer that may include three orthogonal accelerometers formeasuring acceleration in three dimensions. The drilling performancesensor 12 is configured to sense one or more physical propertiesassociated with drilling the borehole 2. Non-limiting embodiments of thephysical properties include vibration (such as axial vibration, lateralvibration, and/or torsional vibration), abnormal drill bit motion (suchas drill bit whirl and/or stick slip), gas detection in borehole, andborehole pressure. Non-limiting embodiments of the drilling performancesensor 12 include an accelerometer for measuring vibration and abnormaldrill bit motion, a gas detector, and a pressure sensor. The lithologysensor 13 is configured to sense a lithology of the formation layer thatis being drilled. Non-limiting embodiments of the lithology sensor 13include a natural radiation detector and a neutron tool, which emitsneutrons that interact with the formation layer to generate radiationthat is measured by the tool. Measured radiation is then correlated to atype of lithology.

Still referring to FIG. 1, downhole electronics 14 may be coupled to thesensors 11, 12, and/or 13 and configured to operate these downholesensors, process sensor measurement data obtained downhole, and/or actas an interface with telemetry to communicate data or commands betweenthe downhole sensors and a computer processing system 15 disposed at thesurface of the earth 3. Non-limiting embodiments of the telemetryinclude pulsed-mud and wired drill pipe. Downhole sensor operation anddata processing operations may be performed by the downhole electronics14, the computer processing system 15, or a combination thereof. Thedownhole sensors may be operated continuously as the borehole is beingdrilled or a discrete selected depths in the borehole 2. Surfacedrilling parameters may be sensed by a surface drilling parameter sensor16. Non-limiting embodiments of surface drilling parameters sensed bythe sensor 16 include weight-on-bit, torque applied to the drill string,rotational speed, drilling fluid flow rate, borehole pressure, andborehole gas. The surface drilling parameters may be input into thecomputer processing system 15 for comparison to normal expected valuesand to threshold values, which if exceeded may cause the computerprocessing system to display an alarm to an operator or automaticallyinput new drilling parameters into the drill rig controller 5.

Referring now to FIG. 2, a top view of the surface of the earth wherethe borehole 2 is being drilled is illustrated. FIG. 2 also illustratesseveral offset boreholes 20. The offset boreholes 20 were previouslydrilled into the same or similar formation layers as the formationlayers that are expected to be encountered while drilling the borehole2. Each of the offset boreholes 20 is associated with the drillingparameters that were used to drill each of those boreholes. The offsetborehole drilling parameters include the drilling parameters used fordrilling through each formation layer encountered having a particularlithology, the depth and thickness of each of the formation layershaving the particular lithology, and the corresponding rate ofpenetration or ROP for each of the formation layers having theparticular lithology. Each of the offset boreholes 20 may also beassociated with any drilling dysfunctions that may have been encounteredduring the drilling of the offset boreholes 20 with the associateddrilling parameters. This data may be entered as a data set into aprocessing system such as the computer processing system 15 for example.

It can be appreciated that once the data for the offset boreholedrilling parameters are obtained, a borehole plan may be drafted for theborehole 2 to be drilled. The borehole plan may include a desiredtrajectory or path that the borehole 2 is to follow and the formationlayers (including depth and thickness) that are to be drilled. It can beappreciated that when a dip angle of a formation layer penetrated by anoffset borehole 20 is known, the depth of the formation layer at thesite of the borehole 2 or at points along the desired trajectory may beestimated using geometry and extrapolation techniques.

FIG. 3 is a flow chart for a method 30 for drilling a boreholepenetrating the earth using a drill rig that operates a drill string.Block 31 calls for inputting into a processor (i) drilling parameters asa function of depth used to drill one or more offset boreholes, (ii)rate of penetration as a function of depth using the drilling parametersfor the one or more offset boreholes, and (iii) one or more lithologiesas a function of depth for the one or more offset boreholes.

Block 32 calls for identifying, using the processor, those drillingparameters that correspond to a rate of penetration (ROP) that meets orexceeds a selected ROP threshold for each input lithology to provideidentified drilling parameters. In other words, the drilling parametersthat provided the highest ROP for each particular lithology drilled areidentified so that if a particular lithology is identified for beingdrilled in the new borehole, then those parameters resulting in the ROPmeeting or exceeding the selected ROP threshold for each of the one ormore assumed lithologies in the borehole plan can be used to drill thatparticular lithology. In one or more embodiments, the selected ROPthreshold for each input lithology is the set of drilling parametersthat results in the highest measured or observed ROP. In one or moreembodiments, the selected ROP threshold for each input lithology may beless than the highest measured or observed ROP in order to lessen therisk or likelihood of drilling dysfunctions. In these embodiments, theselected ROP threshold for each of the one or more assumed lithologiesin the borehole plan may be selected in order to minimize the cost perfoot of drilled borehole by balancing the increased cost due todecreasing the ROP from the maximum with the costs saved by decreasingthe number and/or magnitude of drilling dysfunctions. It can beappreciated that an economic analysis based on the particular factorsrelated to the new borehole may be performed in order to determine theselected ROP threshold.

Block 33 calls for correlating a borehole plan comprising one or moreassumed lithologies as a function of depth to the one or morelithologies of the one or more offset boreholes using the processor. Inother words, the borehole plan includes a desired trajectory of theborehole to be drilled and the formation layers, each having anassociated lithology, depth and thickness that are expected to bedrilled along the trajectory. In block 33, the expected lithology ismatched or correlated to a formation layer lithology that wasencountered in one or more of the offset boreholes.

Block 34 calls for sending the identified drilling parameters to a drillrig controller for each of the assumed lithologies in the borehole plan.In one or more embodiments, the sending may include electronically oroptically transmitting the identified parameters to the drill rigcontroller or the sending may include providing the drill rig controllerwith a readable medium having encoded thereon the identified drillparameters and associated depths and depth intervals for which theidentified drilling parameters are to be applied to the drill rig.

Block 35 calls for drilling the borehole with the drill rig using theidentified drilling parameters that provide the ROP that meets orexceeds the selected ROP threshold for each of the one or more assumedlithologies in the borehole plan.

In one or more embodiments of the method 30, the drilling parametersinclude at least one of torque applied to a drill string operated by thedrill rig, weight on bit, drilling fluid flow rate, and drill stringrotational speed.

In one or more embodiments of the method 30, the depth discussed in themethod 30 is the true vertical depth in order to account for a boreholedeviated from the vertical or horizontal boreholes.

In one or more embodiments of the method 30, the method 30 may includeautomatically transmitting identified drilling parameters to a drill rigcontroller for a change in lithology when a depth is reached signifyingthe beginning of an interval of the changed lithology according to theborehole plan.

In one or more embodiments of the method 30, the method 30 may includeidentifying a lithology currently being drilled using a downhole sensordisposed on a drill string drilling the borehole and updating theborehole plan using the lithology identified by the downhole sensor.

In one or more embodiments of the method 30, the method 30 may includeidentifying a location of a drill string drilling the borehole using asensor disposed on the drill string and updating the borehole plan usingthe identified location. The location may include information describingthe depth and azimuthal orientation of points along the path ortrajectory of the drilled borehole so that one of ordinary skill in theart or a processing system can plot the path of the borehole on a map orrecord its position in a data base.

In one or more embodiments of the method 30, the method 30 may includeinputting into the processor any drilling dysfunctions that occurredusing the drilling parameters for the one or more offset boreholes andwherein identifying in Block 32 further includes identifying thosedrilling parameters that have a minimum number of drilling dysfunctionsand/or minimum magnitude of a drilling dysfunction as being identifieddrilling parameters. In one or more embodiments, the drillingdysfunctions may include at least one of vibrations (axial, lateral,and/or rotational) of a drill string operated by the drill rig exceedinga threshold value, torque applied to the drill string exceeding athreshold value, and borehole pressure exceeding a threshold value. Aminimum number of drilling dysfunctions relates to a minimum number oroccurrences of drilling dysfunctions while a minimum magnitude relatesto a minimum amplitude of a drilling dysfunction such as a vibration.Threshold values may be determined by analysis or evaluation of fielddata such that the likelihood or probability of drilling dysfunctionsoccurring (number of occurrences and/or magnitude) is reduced orminimized.

In one or more embodiments of the method 30, the method 30 may includesending an override signal from the processor to the drill rigcontroller based on a drilling performance indicator sensed by adrilling performance sensor. In one or more embodiments, the drillingperformance indicator includes at least one of axial vibration, lateralvibration, torsional vibration, abnormal drill bit motion, gasdetection, and borehole pressure. In one or more embodiments, sendingmay include the processor automatically sending the override signal whenthe drilling performance indicator exceeds a threshold value. In one ormore embodiments, the method 30 may include displaying the drillingperformance indicator to a user and sending may include the userproviding a manual input to the processor for sending the overridesignal based on the displayed performance indicator using a manual inputdevice such as a pushbutton switch for example.

In one or more embodiments of the method 30, the method 30 may include(a) receiving borehole survey information from a borehole survey sensor,the survey information having a borehole trajectory including depth ofthe borehole being drilled and (b) cross-checking the lithology assumedin the drilling parameters with the survey information based on depth.The method 30 may also include updating the drilling parameters based onthe survey information. In one or more embodiments of the method 30, themethod 30 may include comparing the rate of penetration (ROP) assumed bythe identified drilling parameters to the actual ROP sensed by a drillrig sensor and updating the drilling parameters being used when adifference between the assumed ROP and the actual ROP exceeds athreshold value, wherein the updated drilling parameters are based on alithology different from the lithology assumed in the borehole plan. Thethreshold value in this case may account for instrument or sensor errorso that false indications are prevented.

The above disclosed techniques provide several advantages. One advantageis that the ROP may be improved over the ROP resulting from usingconventional techniques to determine drilling parameters. Anotheradvantage is that the number and/or magnitude of drilling dysfunctionsmay be decreased compared to the number and/or magnitude of drillingdysfunctions resulting from using conventional techniques to determinedrilling parameters. Yet another advantage is the total cost of drillingthe borehole may be decreased by both improving the ROP and decreasingthe number and/or magnitude of drilling dysfunctions.

In support of the teachings herein, various analysis components may beused, including a digital and/or an analog system. For example, thedownhole electronics 14, the computer processing system 15, the downholesensors 11, 12 and 13, the drill rig controller 5, or the surfacedrilling parameter sensor 16 may include digital and/or analog systems.The system may have components such as a processor, storage media,memory, input, output, communications link (wired, wireless, pulsed mud,optical or other), user interfaces, software programs, signal processors(digital or analog) and other such components (such as resistors,capacitors, inductors and others) to provide for operation and analysesof the apparatus and methods disclosed herein in any of several mannerswell-appreciated in the art. It is considered that these teachings maybe, but need not be, implemented in conjunction with a set of computerexecutable instructions stored on a non-transitory computer readablemedium, including memory (ROMs, RAMs), optical (CD-ROMs), or magnetic(disks, hard drives), or any other type that when executed causes acomputer to implement the method of the present invention. Theseinstructions may provide for equipment operation, control, datacollection and analysis and other functions deemed relevant by a systemdesigner, owner, user or other such personnel, in addition to thefunctions described in this disclosure.

Further, various other components may be included and called upon forproviding for aspects of the teachings herein. For example, a powersupply (e.g., at least one of a generator, a remote supply and abattery), cooling component, heating component, magnet, electromagnet,sensor, electrode, transmitter, receiver, transceiver, antenna,controller, optical unit, electrical unit or electromechanical unit maybe included in support of the various aspects discussed herein or insupport of other functions beyond this disclosure.

The flow diagrams depicted herein are just examples. There may be manyvariations to these diagrams or the steps (or operations) describedtherein without departing from the spirit of the invention. Forinstance, the steps may be performed in a differing order, or steps maybe added, deleted or modified. All of these variations are considered apart of the claimed invention.

Elements of the embodiments have been introduced with either thearticles “a” or “an.” The articles are intended to mean that there areone or more of the elements. The terms “including” and “having” areintended to be inclusive such that there may be additional elementsother than the elements listed. The conjunction “or” when used with alist of at least two terms is intended to mean any term or combinationof terms. The term “configured” relates to a structural limitation of anapparatus that allows the apparatus to perform the task or function forwhich the apparatus is configured.

While one or more embodiments have been shown and described,modifications and substitutions may be made thereto without departingfrom the spirit and scope of the invention. Accordingly, it is to beunderstood that the present invention has been described by way ofillustrations and not limitation.

It will be recognized that the various components or technologies mayprovide certain necessary or beneficial functionality or features.Accordingly, these functions and features as may be needed in support ofthe appended claims and variations thereof, are recognized as beinginherently included as a part of the teachings herein and a part of theinvention disclosed.

While the invention has been described with reference to exemplaryembodiments, it will be understood that various changes may be made andequivalents may be substituted for elements thereof without departingfrom the scope of the invention. In addition, many modifications will beappreciated to adapt a particular instrument, situation or material tothe teachings of the invention without departing from the essentialscope thereof. Therefore, it is intended that the invention not belimited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A method for drilling a borehole penetrating theearth using a drill rig that operates a drill string, the methodcomprising: inputting into a processor (i) drilling parameters as afunction of depth used to drill one or more offset boreholes, (ii) rateof penetration using the drilling parameters for the one or more offsetboreholes, (iii) any drilling dysfunctions that occurred using thedrilling parameters for the one or more offset boreholes, and (iv) oneor more lithologies as a function of depth for the one or more offsetboreholes; identifying, using the processor, those drilling parametersthat correspond to a rate of penetration (ROP) that meets or exceeds aselected ROP threshold for each input lithology to provide identifieddrilling parameters and/or to a minimum number of drill dysfunctions orminimum magnitude of a drilling dysfunction to provide identifieddrilling parameters; correlating a borehole plan comprising a boreholepath to be drilled and one or more assumed lithologies as a function ofdepth to the one or more lithologies of the one or more offsetboreholes; automatically transmitting identified drilling parameters toa drill rig controller for a change in lithology when a depth is reachedsignifying the beginning of an interval of the changed lithologyaccording to the borehole plan; drilling the borehole with the drill rigusing the identified drilling parameters that provide the ROP that meetsor exceeds the selected ROP threshold for each of the one or moreassumed lithologies in the borehole plan; and sending an override signalfrom the processor to the drill rig controller based on a drillingperformance indicator sensed by a drilling performance sensor.
 2. Themethod according to claim 1, further comprising (a) receiving boreholesurvey information from a borehole survey sensor, the survey informationcomprising a borehole trajectory including depth of the borehole beingdrilled and (b) cross-checking the lithology assumed in the drillingparameters with the survey information based on depth.
 3. The methodaccording to claim 2, further comprising updating the drillingparameters based on the survey information.
 4. The method according toclaim 2, further comprising comparing the rate of penetration (ROP)assumed by the identified drilling parameters to the actual ROP sensedby a drill rig sensor and updating the drilling parameters being usedwhen a difference between the assumed ROP and the actual ROP exceeds athreshold value.
 5. The method according to claim 4, wherein the updateddrilling parameters are based on a lithology different from thelithology assumed in the borehole plan.
 6. The method according to claim2, wherein the borehole survey sensor is disposed on the drill string.7. The method according to claim 1, further comprising inputting intothe processor any drilling dysfunctions that occurred using the drillingparameters for the one or more offset boreholes and wherein identifyingfurther comprises identifying those drilling parameters that have aminimum number of drill dysfunctions or minimum magnitude of a drillingdysfunction as being identified drilling parameters.
 8. The methodaccording to claim 7, wherein drilling dysfunctions comprise at leastone of vibrations of a drill string operated by the drill rig exceedinga threshold value, torque applied to the drill string exceeding athreshold value, and borehole pressure exceeding a threshold value. 9.The method according to claim 1, wherein the drilling parameterscomprise at least one of torque applied to a drill string operated bythe drill rig, weight on bit, drilling fluid flow rate, and drill stringrotational speed.
 10. The method according to claim 1, wherein the depthis true vertical depth.
 11. The method according to claim 1, furthercomprising identifying a lithology currently being drilled using adownhole sensor disposed on the drill string drilling the borehole andupdating the borehole plan using the lithology identified by thedownhole sensor.
 12. The method according to claim 1, further comprisingidentifying a location of a drill string drilling the borehole using asensor disposed on the drill string and updating the borehole plan usingthe identified location.
 13. The method according to claim 1, whereinthe drilling performance indicator comprises at least one of axialvibration, lateral vibration, torsional vibration, abnormal drill bitmotion, gas detection, and borehole pressure.
 14. The method accordingto claim 1, wherein sending comprises the processor automaticallysending the override signal when the drilling performance indicatorexceeds a threshold value.
 15. The method according to claim 1, furthercomprising displaying the drilling performance indicator to a user andwherein sending comprises the user providing a manual input to theprocessor for sending the override signal based on the displayedperformance indicator.
 16. The method according to claim 1, wherein thedrilling performance sensor is disposed on the drill string and thedrilling performance indicator is measured in the borehole.